Mishnah, also spelled Mishna (Hebrew: “Repeated Study”), plural Mishnayot, is the oldest authoritative postbiblical collection and codification of Jewish oral laws, systematically compiled by numerous scholars (called tannaim) over a period of about two centuries. "Mishnah" is a noun formed from the verb "shanah," which originally meant "to repeat". It has the same meaning as the Aramaic "matnita," derived from "teni" or "tena." Therefore its meaning is "instruction," the teaching and learning of the tradition. The verb "shanah," acquired in post-Biblical Hebrew the special force of "to teach" and "to learn" that which was not transmitted in writing but only orally; the development of this connotation being due to the fact that the retention of teachings handed down by word of mouth was possible only by frequent recitation. The codification was given final form early in A.D. the 3rd century by Judah ha-Nasi (about 210).
Mishna | Jewish laws | Britannica Encyclopedia (britannica.com)
Mishna (construct state, Mishnat): By: Executive Committee of the Editorial Board., Jacob Zallel Lauterbach - Jewish Encyclopedia (jewishencyclopedia.com)